Helen hits the burglar and then drives away in the same direction. She tells Peter she was driving by the factory road in the back. Minutes later Officer Johnson told Matthews that there were two ways in and out, but the rear gate had been locked for hours. Helen would have had to leave the same way she arrived, but did not do so. Peter and Helen as well as the ambulance are then shown arriving at the plant from the direction of the locked gate.
Matthews tells Helen that hit and run is a felony and if the man dies she would be charged with manslaughter. States require a driver involved in an accident to immediately report it. Since there were no cell phones in 1955 and the business where the accident happened appeared to be closed, by Helen driving 4 blocks to her home and reporting the accident and then immediately returning, this negated her culpability for hit and run. Manslaughter charges require the driver to be negligent. As the accident was depicted and reported by Helen, the pedestrian was at fault for running into the road when it was impossible for the driver to yield, so there would be no basis for a manslaughter charge.
When Dan Mathews makes a phone call from Joe Barton's place he dials only 6 numbers on the phone, not 7.